Neurotrauma and neurodegenerative diseases affect millions of people annually. A common pathology is the loss of long-distance connections, specifically axons connecting regions of the central nervous system or relaying peripheral signals. This axonal degeneration may result in permanent deficits. Due to the lack of spontaneous regenerative capability of long-distance axonal connections in the central and peripheral nervous system, researchers are developing tissue engineered constructs to reverse the effects of trauma or neurodegenerative disease. Successful application involves the integration of engineered living tissue to directly restore lost function or create a more suitable environment for regeneration. To facilitate axon regeneration, we utilize novel tissue engineered nerve grafts (TENGs) comprised of long, aligned axonal tracts generated by stretch-growth, a natural mechanism that is replicated in custom mechano-bioreactors to generate axons of unprecedented lengths in a short period of time. The axonal tracts serve as a living scaffold for neuroregeneration. In previous rodent and swine studies, the living axonal tracts in TENGs have been seen to serve as guidance paths to direct regenerating axons, with regenerating host axons growing directly along transplanted TENG axons, demonstrating direct axon mediated axon regeneration (AMAR). However, the molecular mediators responsible for this phenomenon remain unknown, yet are crucial to further enhance this technology. Therefore, during my fellowship tenure, I intend to elucidate the molecular mediators primarily responsible for AMAR by developing an in vitro test bed and utilizing an innovative in vivo axon regeneration paradigm to systematically elucidate the cellular factors primarily driving AMAR. Specifically, I hypothesiz that juxtacrine signaling - a combination of axon-surface cues and concomitant intimate presentation of soluble factors - drives AMAR. This hypothesis will be tested through immunohistochemistry, confocal microscopy, super resolution microscopy, as well as electrophysiological analyses for functional recovery in rodents. Determining the precise juxtacrine signaling involved in AMAR is broadly applicable to improving peripheral as well as central nervous system repair and regeneration, thus ultimately improving neurological recovery following a range of traumatic injuries or neurodegenerative diseases.